GDDR3 was specified in 2002, while GDDR5 was first demonstrated in 2007.
If your motherboard is so old that it doesn't support a 2007 standard, you shouldn't use it. You will run into a host of other issues that I won't even bother to mention.
Honestly hashrate will be the last of your problem.
Just get a cheap, up-to-date motherboard with a Celeron CPU.
not much issues as I can put the 580 in and it will run pubg with 0 problems but I guess I should change my question to Has anyone run a ddr5 card on a ddr3 mobo pci and had any loss of hash